Acute effect of HIIT on testosterone and cortisol levels in healthy individuals: A systematic review and meta-analysis.

To determine the acute effect of a single high-intensity interval training (HIIT) session on testosterone and cortisol levels in healthy individuals, a systematic search of studies was conducted in MEDLINE and Web of Science databases from inception to February 2020. Meta-analyses were performed to establish the acute effect of HIIT on testosterone and cortisol levels immediately after a single HIIT session, after 30 minutes, and 60 minutes (primary outcomes) and after 120 minutes, 180 minutes, and 24h (secondary outcomes, only for pre-post intervention groups). Potential effect-size modifiers were assessed by meta-regression analyses and analyses of variance. Study quality was assessed using the Cochrane's risk of bias tool and the Physiotherapy Evidence Database scale. The meta-analyses of 10 controlled studies (213 participants) and 50 pre-post intervention groups (677 participants) revealed a significant increase in testosterone immediately after a single HIIT session (d=0.92 and 0.52, respectively), which disappeared after 30 minutes (d=0.18 and -0.04), and returned to baseline values after 60 minutes (d=-0.37 and -0.16). Significant increases of cortisol were found immediately after (d=2.17 and 0.64), after 30 minutes (d=1.62 and 0.67), and 60 minutes (d=1.32 and 0.27). Testosterone and cortisol levels decreased significantly after 120 minutes (d=-0.48 and -0.95, respectively) and 180 minutes (d=-0.29 and -1.08) and return to baseline values after 24h (d=0.14 and -0.02). HIIT components and participant's characteristics seem to moderate the effect sizes. In conclusion, testosterone and cortisol increase immediately after a single HIIT session, then drop below baseline levels, and finally return to baseline values after 24h. This meta-analysis provides a better understanding of the acute endocrine response to a single HIIT session, which would certainly be valuable for both clinicians and coaches in the prescription of exercise programs to improve health and performance. Testosterone and cortisol may be used as sensitive biomarkers to monitor the anabolic and catabolic response to HIIT. This article is protected by copyright. All rights reserved.